Organotemplate-free synthesis and proton conduction properties of a layered aluminophosphate Na₄[Al₄P₄O₁₈]·H₂O

In the organotemplate-free system, a layered aluminophosphate Na₄[Al₄P₄O₁₈]·H₂O(1) was synthesized with Na⁺ ion as the structure-directing agent under hydrothermal condition. The structure was determined by single-crystal X-ray diffraction, and further characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), inductively coupled plasma(ICP) and thermal gravimetric (TG) analyses. Compound 1 crystallizes in the monoclinic space group P2₁/c with a=1.00887(9) nm, b=0.86747(8) nm, c=0.97580(9) nm, V=0.77387(12) nm³, and Z=2, and its framework consists of AlO₅ and PO₄ units. Compound 1 possesses high thermal stability, and the crystal structure remains unchanged after calcination at 400℃ in air. The proton conductivity measurement gives that compound 1 possesses excellent conductivity with σ the value of 1.19×10^-3 S/cm when immersed in water at 55℃, which is higher than those of traditional zeolitic materials.